PYY is released during a meal from L-cells in the distal small intestine and the colon. PYY is known to have peripheral effects in the gastrointestinal (GI) tract and also act centrally as a satiety signal. PYY is naturally secreted as a 36 amino acid peptide (PYY(1-36)) with a C-terminal amide but is cleaved to PYY(3-36) which constitutes approximately 50% of the circulating PYY. The enzyme responsible for the degradation is dipeptidyl peptidase IV (DPPIV). PYY(3-36) is rapidly eliminated by proteases and other clearance mechanisms. The half-life of PYY(3-36) has been reported to be <30 minutes in pigs. Thus, PYY displays suboptimal pharmacokinetic properties, meaning that the peptide has to be administered at least twice daily.
Whereas PYY(1-36) activates Y1, Y2 and Y5 receptors with very little selectivity and the Y4 receptor slightly less, the DPPIV processed PYY(3-36) displays increased selectivity for the Y2 receptor over Y1, Y4 and Y5 receptors, albeit some Y1 and Y5 affinity is retained. Y2 receptor activation is known to decrease appetite and food intake whereas Y1 and Y5 receptor activation leads to an increase in appetite and food intake. Furthermore, Y1 and Y5 receptor activation may lead to an increase in blood pressure.
PYY(3-36) has been suggested for use in the treatment of obesity and associated diseases based on the demonstrated effects of certain of these peptides in animal models and in man, and on the fact that obese people have low basal levels of PYY as well as lower meal responses of this peptide. Furthermore, Y2 agonists have been demonstrated to have anti-secretory and pro-absorptive effects in the gastro-intestinal (GI) tract. The potential use of Y2 agonists in the treatment of a number of gastro-intestinal disorders has been suggested.
Based on demonstrated effects in e.g. Zucker rats and Diet-Induced Obese (DIO) mice Y2 selective PYY(3-36) analogues have a positive effect on glucose metabolism and are thus suggested to be used for the treatment of diabetes.
WO 2009/138511 relates to long-acting Y2 and/or Y4 receptor agonists. WO 2011/033068 relates to PYY analogues stabilised against C-terminal proteolytic breakdown. WO 2011/058165 relates to Y2 receptor agonists with protracted pharmacokinetic properties.
For the treatment of conditions responsive to Y receptor modulation such as obesity and diabetes it would be attractive to use PYY analogues which are specific for the Y receptor subtype Y2 and importantly also display protracted pharmacokinetic properties and as such can be used in a dosing regimen with lower frequency of administration than PYY or PYY(3-36).